The present invention generally relates to a gear type transmission unit or speed change gear unit, and more particularly, to a construction thereof around a bearing retainer mounted at a front wall portion of a housing of the transmission unit, and also to a lubricating arrangement in an extension housing provided at the rear end portion of the transmission unit housing.
Generally, in a gear type transmission unit for a motor vehicle, a bearing retainer is mounted on an opening formed at a front wall of a transmission unit housing so as to rotatably support an input shaft through a bearing held in said bearing retainer, while one end of said input shaft is connected to an output shaft of said transmission unit through another bearing for relative rotation therewith.
Incidentally, in a transmission unit of the above described type, it is so arranged that lubricating oil collected at the bottom portion of the transmission unit housing is raised or picked up through rotation of various speed changing gears provided in said housing so as to be fed to respective lubricating portions such as the bearing portions, etc. referred to earlier, but in the above case, there is a tendency that the lubricating oil is not sufficiently distributed to the vicinity of such bearing portions due to the positional relation thereof.
In order to overcome the inconvenience as described above, there has conventionally been proposed a technique disclosed, for example, in Japanese Utility Model Laid-Open Application Jikkaisho No. 56-146159 in which an oil receiver is provided at the side of a speed change gear mechanism, on a front wall of the transmission unit housing, while oil holes for communicating the peripheral portion of the bearing held in the bearing retainer for supporting the input shaft, with the oil receiver are formed in said front wall so that the oil picked up in the transmission unit housing is introduced into the bearings through said oil holes. By the above arrangement, since the lubricating oil is positively guided even to the peripheral portions of the bearings at the front wall side of the transmission unit housing where such lubricating oil is rather difficult to be distributed, insufficient lubrication for such bearings may be eliminated.
However, since the technique disclosed in said Japanese Utility Model Laid-Open Application Jikkaisho No. 56-146159 requires to integrally form the oil holes and oil receiver on a large sized workpiece such as the transmission unit housing, there is such a problem that processing thereof is relatively difficult.
Meanwhile, for example, in a manually operated transmission unit for a motor vehicle, an extension housing is provided at one end of the transmission unit housing, and at the rear end portion of said extension housing, a front end of a propeller shaft is relatively movable coupled to a rear end of an output shaft. At the front end side of the extension housing, the output shaft is journalled at its intermediate portion through a bearing provided at the forward wall of said extension housing, while at the rear end side of said housing, the front end of said propeller shaft, i.e., the coupling portion between said propeller shaft and the output shaft is journalled through a sleeve or the like. In the above case, to achieve sufficient lubrication for the above two bearing portions, it is also arranged that the lubricating oil collected at the bottom portion of the transmission unit housing and picked up by the speed changing gears is supplied to the bearing at the front end side of the extension housing. However, in the case of the bearing portion at the rear end of said extension housing which is located at a position relatively spaced from the transmission unit housing, it is impossible to spread splashes of the lubricating oil up to such bearing portion merely through picking up of the oil by the speed changing gears, and therefore, it is necessary to separately provide some other means to lead the lubricating oil to said bearing portion.
As one example of such lubricating oil leading means referred to above, there has conventionally been disclosed in Japanese Utility Model Laid-Open Application Jikkaisho No. 58-135557, a lubricating device in which, in a construction wherein a laterally projecting cylindrical portion accommodating therein a rotatin shaft through a bearing is provided on a transmission unit case containing therein speed changing gears and lubricating oil, at a position above the level of the lubricating oil, there is provided a shielding member projecting upwardly from the bottom face of the cylindrical portion by a predetermined distance at the end portion of said cylindrical portion adjacent to the side of the transmission unit case. By the above arrangement, the lubricating oil flowing into the cylindrical portion by the picking up action of the speed changing gears is blocked by said shielding member so as to be collected in said cylindrical portion, and therefore, the lubricating oil may be sufficiently supplied into the forward end portion of the cylindrical portion spaced from the transmission unit casing for positive lubrication of the bearing for the rotating shaft located at such forward end portion.
However, when the means as described above is employed for the extended portion referred to earlier, the number of parts is increased by the provision of the shielding member, thus resulting in a cost increase to that extent.
In addition, in the conventional arrangements, there has been known such a construction in which a rib or conduit for introduction of the lubricating oil is provided at a ceiling portion in the extension housing so as to lead the lubricating oil picked up within the transmission unit housing toward the bearing portion at the rear end portion of the extension housing through the rib or conduit. However, in the case of the rib, the lubricating oil tends to drip off before reaching the bearing portion, thus resulting in an insufficient lubrication, while in the case of the conduit, the structure at the ceiling portion of the extension housing is undesirably complicated.